Weed destroying composition



Patented July 24, 1934 UNITED STATES PATENT OFFICE WEED DESTROYINGCOMPOSITION Carlton R. Rose, Berkeley, Calif.

No Drawing. Application July 31, 1933, Serial No. 683,095

3 Claims. (Cl. 167-45) I'his is a continuation in part of my applicationmay result from the amount of water used in the Serial No. 577,153,filed November 24th, 1931. final dilution of the mixture required forspray- My invention relates to chemical compositions ing; or thenecessary proportion of the sulphuric for destroying undesirablevegetation. acid may be secured in the initial proportions of I Suchcompositions are preferably applied by the two acids in a mixture, thedilution of which 60 spraying; and since the leaves of the plants pribywater to form the final spray solution being marily are exposed tospray, there must be such proportionally regulated. Thus my invention inleaf absorption as will carry the destructive agent its preferred formmay be stated further to conto the plant roots, for it is only bydestroying the sist in a practical commercial product adapted l rootsthat complete success can be had. for spray dilution and comprising asubstantially In the numerous weed destroying compositions 75% solutionof arsenic acid mixed in substanheretofore used; arsenic has been aspecially fatially equal volume with a substantially 99% soluvored andcommon toxic agent. Various acids tionof sulphuric acid. Though mycomposition have also been used, noticeably, sulphuric acid, iseifective for destroying many weeds and other and in many compositionsboth arsenic and supundesirable vegetation, its application to anddeplementary acid have been ingredients in the structive result upon theperennial plant morning-'1 mixture. Although, in almost all instances,the glory will best illustrate its nature and disclose form of arsenicso used has been the trioxid, itas asolution of the problem confrontingfarmarsenous acid (As203), a stronger form, the peners whose land isinfested with this noxious weed.

- toxid, arsenic acid, (As205) appears in the prior Morning-glory has aroot system extending art for suggested use in weed killers, eitheralone from 15 to 20 feet or more into the ground, and or combined withanother acid among w ich sulwith many lateral roots running horizontallyin phuric acid is mentioned, though, as far as I am all directions.Several arsenic compositions preaware, the specific combinativeproportions of viously used by me both with and without another arsenicacid and sulphuric acid, essential for sucacid, some even havingsulphuric acid, killed l cess, as I shall herein demonstrate, have neverthe main tap-root to a depth of only three or been disclosed nor usedprior to my invention. I four feet, the lateral vroots usually escapinghave found from long and extensive experience damage. The next yearthese lateral roots and that weed destroying compositions comprising allthe tap roots which were not killed to the arsenous acid (AS203) and asupplemental acid, five foot level sent up new shoots and the weed 85whether such last named acid be sulphuric acid infestation was nearly-asbad as it was original- (H2SO4), or otherwise, are not successful; andthe ly. I found that to be efiicient a weed killer must same is true ofthe use of arsenic acid (AS205) kill the tap-roots to at least a depthof five feet alone,'or even when combined with H2804, unless and killall the laterals above that level. Exthe latter ingredient be present inproper properiments leading to this discovery involved not 90 portion, acondition which, as I have stated above only repeated changes andmodifications of prehas never, as far as I know, been disclosed or viousformulas, but also required considerable tried. labor in that holes hadto be dug to at least six It is in this discovery of the criticalproportion feet to determine the depth of the root kills. I 40 of thesulphuric acid in an arsenic acid compofound in the course of theseexperiments that 95 sition, that my present invention resides. byincreasing the amount of the oxidizing agent, The object of my inventionis to insure the pernamely the arsenic ingredient, there was an immanentdestruction of the plant by depth of peneprovement in effectiveness,though even then it tration of the composition adapted to effectuallydid not occur to me that if arsenic acid (AS205) V kill the roots insuch measure that revival of the were used instead of arsenous acid(AS203) a 100 plant is practically impossible. still further improvementmight result, for I such depth of penetration I have found, and had manytimes tried arsenic acid and found have satisfactorily demonstrated byextensive use, it worthless. Nevertheless I was led to the conis madepossible by the critical proportion of the clusion that the killingagent should be arsenic sulphuric acid ingredient of the composition. Myacid and that it could be effective only because invention may thereforebe stated to consist in a of the presence of sulphuric acid. It thenrespray solution of a mixture comprising arsenic mained to find theproper proportions. acid and sulphuric acid in such proportions that Insubsequent experiments, various proportions said spray solution shallcontain at least 1% sulof sulphuric acid and arsenic acid were used, andphuric acid by weight. Such a spray solution the results were all judgedby the kill obtained below the five root level, including the lateralroots. From these experiments I discovered that the percentage ofsulphuric acid in the spray mixture was an important factor. By thespray mixture, I mean the solution obtained by dilution with water andused as a spray. In short, enough sulphuric acid should be mixed witharsenic acid, so that when this mixture should be diluted with water,the resultant spray solution would be highly acid, at least 1% sulphuricacid or higher. No matter how much arsenic acid was in the spraymixture, if the sulphuric acid were low, the root kill would be poor, afact which was firmly established.

As I have stated my experiments showed that arsenic acid by itself isworthless, and that sulphuric acid by itself is worthless, but that whenthese two chemicals are combined in the proper proportions, an efiectiveweed killer is formed, one that will kill not merely the tops of theweeds, but will completely kill the main taproots or a perennial to adepth of five feet at least and all the laterals above that depth.

For a clearer understanding of the proper proportions upon which mypresent composition is based and for which a patent is sought, 1 givethe following data in tabular form:

Mixture Resulting Bnl- Spray phuric solul) Dil ti 1 on s: n 0 so I 4 uon 11 percent peroen by vol- (99%) water by Results time percent A3105weight by content volume H180 Percent Percent Percent l 90 10 1 in l001.2% 0. 18 Very poor 2 90 10 l in l0l0.0% 1. 5 air. 3 75 25 l in mil-1.00%0. 44 Not good 4 75 25 l in 50-l.9l% 0. 81 Better. 5 66% 33% 1 inl00-0.88% 0. 58 Not good 6 66% 33% l n fill-1.70% 1. 14 Good. 7 50 50 lml000.65% 0.87 Not 00d 8 50 l in 750.87% 1. 16 Go 9 50 50 1 inBil-1.27% 1. Excellent 10 100 Nil Altli pro por- Very poor one. 11 N11100 All propor- Very poor tions. 1

From this it will be seen that the higher percentages of sulphuric acidin the spray solution yield the better results. In #1 and #9, thearsenic acid content is about the same, but when only 0.18% sulphuricacid is present as in #1, the result is a failure; but when as in #9 itis 1.70% the result is perfect. Furthermore, comparing #5 and #8 in bothof which the arsenic acid content is nearly the same, the result isimproved by a higher sulphuric acid content. Again, comparing #4 and #9it will be seen that in #4 the arsenic acid content is much higher thanin #9 but the result is not as good because the sulphuric acid contentis too low, while in #9 the result is perfect, as above stated.

As the best commercial product, I have adopted the 5050 combination. Bydiluting this mixture with 50 parts of water a spray solution isobtained which contains sufiicient arsenic acid and sulphuric acid,though it may be pointed out that even a more economical mixture may behad by increasing the sulphuric acid content and lowering the arsenicacid content, since the latter is more expensive than the former. I havealso adopted for practical purposes the preliminary mixing of the twoacid ingredients in equal volume solutions, one being a 15% solution ofarsenic acid and the other a 99% solution of sulphuric acid, though, asI have pointed out, since the high sulphuric acid content is thecritical factor in making the arsenic acid efiective as a weed killer,the proportion of the sulphuric acid in the spray solution subsequentlymade by Water dilution must contain at least 1% sulphuric acid byweight.

I claim:

1. A weed destroying concentrate comprising a mixture of arsenic acidand sulphuric acid whereby said mixture when diluted with sufiicientwater will yield a spray solution containing sufficient arsenic acid byweight to be herbicidal and at least one percent sulphuric acid byweight to obtain the necessary depth of penetration resulting in thekilling of the weed roots.

2. A weed destroying composition comprising a substantially solution ofarsenic acid mixed in substantially equal volume with a substantially99% solution of sulphuric acid, whereby depth of penetration resultingin the killing of the roots is obtained.

3. A weed destroying composition consisting of a mixture insubstantially equal volume of a substantially 75% solution of arsenicacid and a substantially 99% solution of sulphuric acid, diluted withwater in sufiicient volume to form a spray solution containing at least1% sulphuric acid by weight, whereby depth of penetration resulting inthe killing of the roots is obtained.

CARLTON R. ROSE.

